Low parental numeracy and severe asthma exacerbations in a prospective study of Puerto Rican youth

Abstract

Background:

Numeracy is the mathematical knowledge required to understand and act upon instructions from healthcare providers. Whether persistently low parental numeracy is linked to childhood asthma exacerbations is unknown.

Objective:

To examine whether low parental numeracy at two timepoints is associated with asthma exacerbations and worse lung function in Puerto Rican youth.

Methods:

Prospective study of 225 youth with asthma in San Juan (PR) who participated in two visits ~5.3 years apart, the first at ages 6–14 years and the second at ages 9–20 years. Parental numeracy was assessed with a modified version of the Asthma Numeracy Questionnaire (score range=0–3 points), and persistently low parental numeracy was defined as a score ≤1 point at both visits. Asthma exacerbation outcomes included ≥1 emergency department (ED) visit, ≥1 hospitalization, and ≥1 severe exacerbation (≥1 ED visit or ≥1 hospitalization) for asthma in the year prior to the second visit. Spirometry was conducted using an EasyOne spirometer (NDD Medical Technologies, Andover, MA).

Results:

In an analysis adjusting for age, sex, parental education, use of inhaled corticosteroids, and the time between study visits, persistently low parental numeracy was associated with ≥1 ED visit for asthma (odds ratio [OR]=2.17, 95% confidence interval [CI]=1.10–4.26), ≥1 hospitalization for asthma (OR=3.92, 95% CI=1.42–10.84) and ≥1 severe asthma exacerbation (OR=1.99, 95% CI=1.01–3.87) in the year prior to the follow-up visit. Persistently low parental numeracy was not significantly associated with change in lung function measures.

Conclusion:

Persistently low parental numeracy is associated with asthma exacerbation outcomes in Puerto Rican youth.

INTRODUCTION

Asthma is the most common chronic disease of childhood, affecting approximately 4.2 million children in the United States (U.S.)¹. In 2019, childhood asthma led to 790,478 visits to the emergency department (ED) and 64,525 hospitalizations, causing suffering for patients and their families while posing substantial costs to healthcare systems¹.

Puerto Rican youth in the continental U.S. and the island of Puerto Rico are more likely to have asthma and to require a visit to the ED or be hospitalized for asthma than non-Hispanic whites and members of other racial or ethnic groups^2–4. Such high asthma burden is multifactorial and likely due to risk factors including economic deprivation and low health literacy.

Health literacy can be defined as the ability to obtain and understand basic information required to make appropriate health decisions⁵. Health literacy includes not only verbal and writing communication skills but also numeracy, the mathematical knowledge required to understand and act upon instructions given by healthcare providers. In caring for children with asthma, parents are primarily responsible for following treatment instructions, and thus parental numeracy (e.g., understanding that four tablets of prednisone at a dose of 10 mg result in a total prednisone dose of 40 mg) could impact management of childhood asthma. Compared with non-Hispanic white adults, Hispanic adults have been shown to have lower numeracy (e.g., 45% vs. 20% in a nationwide U.S. survey)⁶, a knowledge gap that may be partly explained by limited access to math and science classes during their school years⁷.

Cross-sectional studies of adults with asthma have linked higher numeracy to lower morbidity and higher asthma-related quality of life^5,8. Consistent with those findings in adults, we previously reported that low parental numeracy was associated with visits to the ED or urgent care for asthma in a cross-sectional study of 351 Puerto Rican children aged 6 to 14 years⁹. Based on those results, we hypothesized that low parental numeracy persisting over a period of ~5.3 years would lead to an increased risk of asthma exacerbations and worse lung function over time. We tested this hypothesis in a prospective study of Puerto Rican youth living in the island of Puerto Rico.

METHODS

Study population

Subject recruitment and the study protocol for the PROspective study of Puerto Rican youth and Asthma (PROPRA) have been described elsewhere¹⁰. All participants completed an initial (baseline) visit at ages 6 to 14 years and a follow-up visit at ages 9 to 20 years. The baseline visit was part of the Puerto Rico Genetics of Asthma and Lifestyle Study (PR-GOAL)¹¹. For subject recruitment in PR-GOAL, primary sampling units (PSUs) were randomly selected neighborhood clusters based on the 2000 U.S. Census, and secondary sampling units were randomly selected households within each PSU. A household was eligible if ≥1 resident was 6–14 years old. A total of 6,401 households selected for inclusion were contacted. Of these, 1,111 households had ≥1 child who met inclusion criteria other than age (four Puerto Rican grandparents and residence in the same household for ≥1 year). Of these 1,111 households, 438 (39.4%) had ≥1 eligible child with asthma (defined as physician-diagnosed asthma and wheeze in the prior year). From these 438 households, one child with asthma was selected (at random if there was more than one such child). Similarly, only one child without asthma (a control subject, having neither physician-diagnosed asthma nor wheeze in the prior year) was randomly selected from the remaining 673 households. To reach our target sample size (~700 children), we randomly selected and attempted to enroll 783 of the 1,111 eligible children. Parents of 105 (13.4%) of these 783 children refused to participate or could not be reached, leaving 678 study participants (351 children with asthma and 327 controls). The second or follow-up study visit for PROPRA was part of the Epigenetic Variation and Childhood Asthma in Puerto Ricans Study (EVA-PR). Subject recruitment for EVA-PR was conducted from February 2014 to May 2017 and included 543 Puerto Rican youth ages 9 to 20 years with (n=269) and without (n=274) asthma, selected from the 1,111 households eligible for PR-GOAL¹².

Of the 269 participants with asthma at the follow-up visit (in EVA-PR), 225 (83.6%) had participated in the baseline visit in PR-GOAL and are thus included in the current analysis, which focuses on severe disease exacerbations and change in lung function measures in youth with asthma. The study was approved by the IRBs of the University of Puerto Rico and the University of Pittsburgh. Written parental consent and child assent were obtained for participants under 18 years old, and written consent was obtained from participants 18 years and older.

Study procedures

All participants completed a protocol including administration of questionnaires (in Spanish) and spirometry at both the baseline and follow-up visits. One of the child’s caretakers (usually [>93%] the mother) completed a questionnaire on demographics, the child’s general and respiratory health, and family history¹³; and a slightly modified version of the Asthma Numeracy Questionnaire (ANQ), a four-item validated test that uses arithmetic or percentage-based statements or questions that patients with asthma might encounter during a clinic visit¹⁴. As in prior work⁹, we replaced two of the original questions in the ANQ with one about weight because peak flow meters are rarely used in Puerto Rico (see eTable 1 in the eSupplement). The number of correct responses in the modified ANQ (mANQ) ranges from 0 to 3, and parental numeracy was treated as a binary variable (≤1 (low) vs. 2–3 (not low)), based on the distribution of correct responses in the mANQ at the two study visits (Figure 1).

Figure 1.

Percentage of number of correct responses in the modified Asthma Numeracy Questionnaire administered to parents of 406 Puerto Rican youth at the two study visits in PROPRA (PROspective study of Puerto Rican youth and Asthma).

Height and weight were measured to the nearest centimeter and kilogram, respectively. Spirometry was conducted with an EasyOne spirometer (NDD Medical Technologies, Andover, Mass) according to American Thoracic Society and European Respiratory Society recommendations modified for children¹⁵. All participants had to be free of respiratory illnesses for at least four weeks and were instructed to (when possible) avoid the use of inhaled short-acting bronchodilators for 4–6 hours and that of long-acting bronchodilators for at least 24 hours before testing. The best results for forced expiratory volume in 1 second (FEV₁) and forced vital capacity (FVC) were selected for data analysis. Percent predicted values for lung function measures at each visit were calculated using the Global Lung Function Initiative [GLI] equations¹⁶, which account for age, sex, and height.

Statistical Analysis

In our primary analysis, persistently low parental numeracy was defined as a binary variable (low parental numeracy at both study visits vs. low parental numeracy at not more than one visit). In a secondary analysis, our control group included participants without low parental numeracy at both visits, and we separately compared three groups to this control group, as follows: 1) low parental numeracy at visit 1 but not at visit 2, 2) low parental numeracy at visit 2 but not at visit 1, and 3) low parental numeracy at both visits.

Our primary outcomes in participants with asthma were core measures of disease exacerbations (≥1 visit to the emergency department (ED) or urgent care for asthma in the prior year and ≥1 hospitalization for asthma in the prior year) at the second study visit, severe exacerbations (defined as ≥1 ED/urgent care visit or ≥1 hospitalization for asthma in the prior year) at the second study visit, and change in FEV₁ or FEV₁/FVC between the two study visits.

All multivariable analyses of asthma exacerbation outcomes and change in lung function measures were adjusted for parental education (at least one parent completed high school vs. none), use of inhaled corticosteroids in the six months prior to the second visit, the time interval between the study visits, and (for asthma outcomes only) age and sex. Other covariates considered for inclusion in the multivariable analysis were measures of socioeconomic status or SES, including type of health insurance (private or employer-based vs. others) and annual household income (< vs. ≥$15,000/year, the median household income in Puerto Rico in 2008–2009); body mass index (BMI) z-score (calculated using CDC growth charts); exposure to second-hand smoke (SHS) in early life (in utero or in the first two year of life) and current SHS exposure in the child’s household. Such covariates remained in the final multivariable models if they were associated at P <0.10 or if they changed the effect estimate (odds ratio [OR] or β coefficient) by ≥10%. Although annual household income and type of health insurance met these criteria, they were highly correlated (collinear) with parental education and could not be all included in the same model. Thus, all models were adjusted for parental education in our primary analysis, with adjustment for either household income or type of health insurance (instead of parental education) in sensitivity analyses. After the final models were built, we tested for interaction between persistently low parental numeracy and selected covariates (sex, parental education, and use of inhaled corticosteroid [ICS]).

All analyses were performed using SAS version 9.4 (SAS Institute, Cary, NC).

RESULTS

Table 1 shows a comparison of the main characteristics of the 225 study participants at the baseline study visit, according to the presence (n=74) or absence (n=151) of low parental numeracy. Compared with participants whose parents did not have low numeracy, those with low parental numeracy were significantly more likely to have lower annual household income and parental education, to lack private or employer-based health insurance, and to have had at least one ED/urgent care visit for asthma and at least one severe asthma exacerbation in the previous year. There were no significant differences in age, sex, parental history of asthma, current SHE exposure, SHS exposure in early life, BMI z-score, lung function measures, or use of inhaled corticosteroid in the prior 6 months between participants with and without low parental numeracy.

Table 1.

Main characteristics of study participants at the baseline study visit, by parental numeracy

Variables	Parental numeracy
	Low† (n=74)	Not low (n=151)
Age (years)	15.7 ± 2.9	15.0 ± 2.9
Female sex	33 (44.6)	63 (41.1)
Annual household income <$15,000	58 (78.4)	77 (51.0)‡
Neither parent graduated from high school	14 (18.9)	12 (8.0)‡
No private or employer-based health insurance	59 (79.7)	89 (58.9)‡
Parental history of asthma	51 (68.9)	95 (63.8)
SHS exposure in early life*	40 (54.1)	68 (45.0)
Current SHS exposure	31 (41.9)	50 (33.1)
Body mass index z-score	0.9 ± 1.0	0.7 ± 1.1
% predicted FEV1	97.7 ± 15.6	95.8 ± 15.2
% predicted FVC	102.7 ± 15.5	101.7 ± 14.2
% predicted FEV1/FVC	94.8 ± 8.4	93.9 ± 8.8
Time interval between study visits (years)	5.4 ± 1.1	5.3 ± 0.9
Use of inhaled corticosteroids, prior 6 months	16 (21.6)	42 (28.6)
≥ 1 ED/urgent care visit for asthma, prior year	35 (47.3)	48 (31.8)‡
≥ 1 hospitalization for asthma, prior year	12 (16.4)	12 (8.0)
≥ 1 severe asthma exacerbation, prior year**	35 (47.3)	51 (33.8)‡

FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; SHS, second-hand smoke; ED, emergency department. Values presented as n (%) for binary variables and as mean ± standard deviation (SD) for continuous variables.

^*Early life=in utero or in the first two years of life.

^**≥1 ED/urgent care visit for asthma or ≥1 hospitalization for asthma in the prior year.

^†A modified asthma numeracy questionnaire score ≤ 1 at the baseline visit

^‡P<0.05 for comparison between groups.

Table 2 displays a comparison of the main characteristics of 225 study participants at the follow-up study visit, according to the presence or absence of persistently low parental numeracy. Compared with participants without persistently low parental numeracy, those whose parents had persistently low numeracy were significantly more likely to have lower annual household income and parental education, to lack private or employer-based health insurance and to have had at least one hospitalization for asthma, but significantly less likely to have used inhaled corticosteroids in the prior six months. There were no significant differences in parental history of asthma, BMI z-score, lung function measures, or any other characteristics between participants with and without persistently low parental numeracy.

Table 2.

Main characteristics of study participants at the second study visit, by persistently low parental numeracy^†

Variables	Parental numeracy†
	Persistently low† (n=62)	Not persistently low (n=163)
Age (years)	15.8 ± 2.9	15.1 ± 2.9
Female sex	24 (38.7)	72 (44.2)
Annual household income < $15,000	50 (80.7)	85 (52.2)‡
Neither parent graduated from high school	13 (21.0)	13 (8.0)‡
No private or employer-based health insurance	50 (80.7)	98 (60.1)‡
Parental history of asthma	34 (54.8)	82 (50.6)
Body mass index z-score	0.96 ± 1.1	0.74 ± 1.1
Second-hand smoke exposure in early life*	33 (53.2)	75 (46.0)
Current second-hand smoke exposure	27 (43.6)	54 (33.1)
% predicted FEV1	97.6 ± 16.1	96.0 ± 15.0
% predicted FVC	102.8 ± 16.1	101.7 ± 14.0
% predicted FEV1/FVC	94.7 ± 8.9	94.0 ± 8.6
Time interval between study visits (years)	5.4 ± 1.1	5.3 ± 1.0
Use of inhaled corticosteroids in the prior 6 months	10 (16.1)	48 (30.2)‡
≥ 1 ED or urgent care visit for asthma, prior year	29 (46.8)	54 (33.1)
≥ 1 hospitalization for asthma in the prior year	12 (19.7)	12 (7.4)‡
≥ 1 severe asthma exacerbation in the prior year**	29 (46.8)	57 (35.0)

FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; ED, emergency department. Values presented as n (%) for binary variables and as mean ± standard deviation (SD) for continuous variables.

^*Early life=in utero or in the first two years of life.

^**≥1 ED/urgent care visit for asthma or ≥1 hospitalization for asthma in the prior year.

^†A modified asthma numeracy questionnaire score ≤ 1 at both study visits.

^‡P<0.05 for comparison between the groups.

The average time interval between the two study visits was ~5.3 (interquartile range=4.7 to 6.1) years. Figure 1 shows that a higher proportion of participants had parents with low numeracy at the baseline visit than at the follow-up visit (64.5% vs. 33%). Table 3 shows the results of the analysis of persistently low parental numeracy and asthma exacerbation outcomes at the second study visit. In a multivariable analysis adjusting for age, sex, parental education, and ICS use in the previous six months, persistently low parental numeracy was significantly associated with 2.17 times higher odds of ≥1 ED or urgent care visit for asthma, 4.21 times higher odds of ≥1 hospitalization for asthma, and twofold higher odds of ≥1 severe asthma exacerbation in the previous year. In this analysis, ICS use in the prior six months was significantly associated with 3.7 to 3.8 times increased odds of each of the asthma exacerbation outcomes. There was no significant evidence of an interaction between persistently low parental numeracy and sex, parental education, or use of ICS in the prior six months (P ≥0.30 in all instances).

Table 3.

Multivariable analysis of persistently low parental numeracy and asthma exacerbation outcomes at the second study visit in 225 study participants.

Covariates	≥ 1 ED or urgent care visit		≥ 1 hospitalization		≥ 1 severe exacerbation*
	OR (95% CI)	P-value	OR (95% CI)	P-value	OR (95% CI)	P-value
Unadjusted
Persistently low parental numeracy	1.77 (0.98, 3.21)	0.06	3.08 (1.30, 7.30)	<0.01	1.63 (0.90, 2.96)	0.10
Adjusted
Persistently low parental numeracy	2.17 (1.10, 4.26)	0.02	3.92 (1.42, 10.84)	<0.01	1.99 (1.01, 3.87)	0.04
No parent graduated from high school	1.75 (0.79, 3.86)	0.17	2.91 (0.89, 9.49)	0.08	1.72 (0.78, 3.79)	0.18
Use of inhaled corticosteroids in the previous 6 months	3.78 (1.93, 7.43)	<0.01	3.52 (1.25, 9.95)	0.01	3.64 (1.86, 7.11)	<0.01

ED, emergency department; OR, odds ratio; CI, confidence interval. All adjusted models were adjusted for age, sex, parental education at the second visit, use of inhaled corticosteroids in the six months prior to the second visit, and the time interval between study visits.

^*Severe exacerbations defined as at least 1 ED or urgent care or a hospitalization due to asthma in the prior year.

^**A modified asthma numeracy questionnaire score ≤ 1 at both study visits.

Because parental education is collinear with household income and type of health insurance, we cannot include all these measures of SES in the same multivariable model. We thus conducted a sensitivity analysis adjusting for household income or type of health insurance instead of parental education, obtaining similar results (Table 4).

Table 4.

Sensitivity analysis of persistently low parental numeracy and asthma exacerbation outcomes at the second visit in 225 study participants

Covariates	≥ 1 ED or urgent care visit		≥ 1 hospitalization		≥ 1 severe exacerbation**
	OR (95% CI)	P-value	OR (95% CI)	P-value	OR (95% CI)	P-value
Model 1
Persistently low parental numeracy*	2.15 (1.10, 4.20)	0.02	3.83 (1.41, 10.40)	<0.01	1.95 (1.00, 3.79)	<0.05
Annual household income < $15,000 at the second visit	1.80 (0.92, 3.55)	0.09	5.59 (1.19, 26.24)	0.03	1.84 (0.95, 3.60)	0.07
Use of inhaled corticosteroids in the previous 6 months	3.71 (1.88, 7.30)	<0.01	3.27 (1.18, 9.08)	0.02	3.58 (1.82, 7.01)	<0.01
Model 2
Persistently low parental numeracy*	2.13 (1.09, 4.15)	0.03	4.12 (1.50, 11.34)	<0.01	1.93 (0.99, 3.74)	0.05
No private or employer-based health Insurance, second visit	2.18 (1.12, 4.27)	0.02	7.54 (1.58, 36.09)	0.02	2.23 (1.15, 4.35)	0.02
Use of inhaled corticosteroids in the previous 6 months	3.87 (1.95, 7.66)	<0.01	3.78 (1.33, 10.73)	0.01	3.73 (1.89, 7.37)	<0.01

ED, emergency department; OR, odds ratio; CI, confidence interval. All models were adjusted for age, sex, type of health insurance at the second study visit, use of inhaled corticosteroids in the six months prior to the second visit, and the time interval between the two study visits.

^*A modified asthma numeracy questionnaire score ≤ 1 at both study visits.

^**At least 1 ED or urgent care visit for asthma or ≥1 hospitalization for asthma in the prior year.

In a secondary analysis, we compared participants with low parental numeracy at one but not both visits (i.e., at visit 1 but not at visit 2, or at visit 2 but not at visit 1) and subjects with low parental numeracy at both visits with subjects whose parents had low parental numeracy at neither visit (eTable 2). Despite small sample size for each of the four parental numeracy groups in this analysis, low parental numeracy at both visits remained significantly associated with ≥1 ED or urgent care visit for asthma and ≥1 hospitalization for asthma, with similar but non-statistically significant results for ≥1 severe asthma exacerbation (P=0.07).

There was no significant association between low parental numeracy and change in any lung function measure between visits 1 and 2 (see eTable 3).

DISCUSSION

We previously showed that low parental numeracy was associated with ED or urgent care visits for asthma in a cross-sectional study of 351 Puerto Rican children with asthma⁹. In the current study of 225 Puerto Rican youth with asthma, low parental numeracy at two visits conducted ~5.3 years apart was significantly associated with asthma exacerbation outcomes (ED or urgent care visits for asthma, hospitalizations for asthma, and severe asthma exacerbations) in the year prior to the follow-up visit but not with change in lung function measures between study visits. To our knowledge, this is the first prospective study of low parental numeracy and asthma outcomes during childhood and adolescence.

The proportion of parents with low numeracy decreased by nearly half between the first and second study visits (from 64.5% to 33%). This could be explained by greater familiarity with the mANQ (despite the relatively long-time interval between visits) or by improved parental (particularly maternal) education. Low parental numeracy at both visits is thus likely a marker of persistently low (and truly worse) numeracy.

Low health literacy has been associated with indicators of worse asthma severity or control (including asthma exacerbation outcomes) in some^9,17 but not all^18,19 prior cross-sectional studies of children, though the two negative studies^18,19 showed that low parental numeracy was associated with worse parental perception of the child’s overall health, lower parental asthma knowledge, or lower parental confidence in their ability to succeed in managing their child’s asthma. In addition to its prospective design, the current study differs from those previously published in that we focused on parental numeracy in a relatively homogenous group of youth at high risk for asthma (Puerto Ricans).

Low numeracy was associated with lifetime ED visits or hospitalizations for asthma in a cross-sectional study of 73 adults with persistent asthma²⁰. Our negative results for lung function in youth are consistent with those of a 26-week prospective study of 284 adults (70% African American and 6% Latinx) with moderate to severe asthma in Philadelphia (PA), in which low asthma-related numeracy at a baseline visit was significantly associated with better asthma-related quality of life but not with FEV₁% predicted, medication adherence, or asthma control²¹. Parental numeracy is required to accomplish tasks such as estimating the correct dose or understanding the risks of side effects from an asthma medication, both of which could affect correct administration of such medications to their children²². Moreover, numeracy may promote change in parental behavior (including information-seeking) and affect healthcare system navigation skills^5,23. In addition, numeracy is closely related to other health literacy skills (i.e., reading, writing, speech, speech comprehension, and cultural and conceptual knowledge) and self-efficacy, which can impact a parent’s ability to use an asthma action plan⁵. Low parental numeracy or literacy could be addressed through literacy- and numeracy-appropriate asthma action plans. For example, a randomized controlled trial of 217 parents of children with asthma ages 2 to 12 years showed that parents who received a low-literacy pictogram- and photograph-based written asthma action plan (n=109) were less likely to make an error in knowledge of daily and rescue medications or in spacer use than parents who received a standard written action plan²³. While findings from that study are promising, they must be cautiously interpreted in the absence of an assessment of asthma outcomes or an analysis adjusted for indicators of SES²³.

We recognize several study limitations. First, selection bias is possible in any observational study. However, selection bias is an unlikely explanation for our results, as there were no significant differences in low parental numeracy or asthma exacerbation outcomes between children with asthma who completed both visits in PROPRA (n=225) and those who were included in the baseline visit but not in the follow-up visit (n=126, see eTable 4). Second, while the ANQ is a validated tool, the modified version used in the current analysis (mANQ) has not been validated. However, we previously showed an association between low parental numeracy and asthma exacerbation outcomes in a cross-sectional analysis using the mANQ⁸. Third, we lacked data on potential mediators of the estimated effect of persistently low numeracy on asthma exacerbations, such as adherence to controller medications. However, our analysis was adjusted for indicators of SES and ICS use, a marker of asthma severity among Puerto Rican children with asthma (see tables 3 and 4). Indeed, the observed association between ICS use and asthma exacerbation outcomes at the second study visit is most likely due to prescription of ICS for children with poorly controlled or more severe disease, as the cost of ICS and other controller medications is not covered by public health insurance plans in Puerto Rico. Fourth, we defined severe asthma exacerbations based on ED/urgent care visits or hospitalizations for asthma and thus may have missed prescription of oral steroids during scheduled visits to physicians’ offices. However, most youth who visit the ED/urgent care or are hospitalized for asthma in Puerto Rico receive systemic steroids, and parents are less likely to forget reporting such events than a steroid prescription from a primary healthcare provider (an infrequent event in our participants, most of whom lack coverage for primary care visits and instead use an acute healthcare setting for asthma exacerbations). Finally, our results may not be generalizable to children in other racial or ethnic groups, though low health literacy or numeracy has been linked to worse asthma severity or control among children in other historically marginalized groups^5,20.

In summary, low parental numeracy at two timepoints ~5.3 years apart was associated with asthma exacerbation outcomes in a cohort of Puerto Rican children and adolescents. Our findings further support interventional studies to test whether literacy- and numeracy-appropriate tools can help parents in high-risk groups (including Puerto Ricans and other marginalized populations) improve the management and outcomes of asthma in their children.

Abbreviations:

ANQ

Asthma Numeracy Questionnaire

BMI

body mass index

CI

confidence interval

ED

emergency department

FEV₁

forced expiratory volume-one second

FVC

forced vital capacity

ICS

inhaled corticosteroid

OR

odds ratio

SHS

second-hand smoke